The present invention is related to a wear protective cover for a chain, and more particularly to a replaceable cover for protecting the bushings of the chain from external wear.
Endless chains, particularly for track-type tractors, have experienced a marked increase in the service life of the pivotally connected pin and bushing joints with the introduction of improved seals and lubricants in the joints. While this has greatly diminished internal wear between the outer surface of the pin and the inner surface of the bushing of each joint, it has not materially affected external wear. Specifically, the outer surface of each bushing is engaged by a sprocket for driving the chain and is subjected to considerable external wear by the relative motion experienced therebetween. External wear of the bushings often progresses until is necessary to replace each worn bushing with a new bushing, which action requires disassembly of the entire chain at considerable expense.
In order to overcome the problem of external wear of the bushings, one proposal has been to employ a sleeve of abrasion-resistant polymer material over each of the bushings. Each sleeve is split along its length in order to fit over its respective bushing and to facilitate its replacement without disassembly of the chain. However, this proposal suffers from the disadvantage that the sleeve is rotatable on the bushing so that the inner surface of the sleeve and the outer surface of the bushing are worn.
Another proposal employs a protective cover consisting of a semicylindrical body which overlaps the usual outer wear surface of each bushing, and an attaching portion integrally connected to the body which is releasably secured to a track shoe. This offers the advantages of convenient replacement of the individual covers without disassembly of the chain and of a nonrotable mount which eliminates the problem of wear between the cover and bushing. On the other hand, this raises another significant problem in that during reverse operation of the chain external forces act on the free end of the cover and separate the cover from the bushing. As a result, earth and sand are forced into the clearance in a manner which accelerates wear or damage to the outer surface of the bushing or which leads to peeling off of the protective cover from the shoe.